Sept. 20, 1963
ISOMERIZATION O F AZIRIDINES
isomer is further evidence for this mechanism. The low yield of olefinic product from the mercaptans listed in Table I1 was previously explained. The lack of olefinic products from the n-butyl sulfonate and nbutyrate ions is probably due to formation of stable a-carbanions. Experimental Reagents.-Lithium, sodium, potassium, rubidium, and cesium tert- butoxides were obtained from t h e Mine Safety Appliance Co. (Callery, Pa.) as t h e sublimed white powders in wax-sealed containers. All samples were a t least 98.5';; pure. Dimethyl sulfoxide and ieit-butyl alcohol were dried and distilled over Linde 1 3 s Molecular Sieves. Gas chromatographic analysis of both solvents indicated the presence of only one compound. Isobutylene, 1-butene, cis- and trans-2-butene, propylene, and butadiene, which were used for g.c. calibration, were all API samples. Most reactants were obtained from either Columbia Organic Chemicals or Matheson Coleman and Bell as reagent grade materials and analyzed for purity by g.c. before use. Materials less than 9Xc,; pure were distilled under a nitrogen atmosphere through a n 18-in. silvered column equipped with a tantalumwire spiral. In the case of the sulfoxides and sulfones, distillation was carried out in the presence of Linde 13X Molecular Sieves t o ensure complete removal of water. XI1 reagents were stored in a nitrogen drybox before use. Preparation of Reaction Mixtures.--Xll base-solvent systems were prepared in a nitrogen drybox equipped with a moisture conductivity cell attachment. Each solution was prepared t o give the desired molarity (0.62 .If) and stored in sealed containers in the drybox. At the desired time, 7 ml. of the standard solution was withdrawn by a pipet and transferred t o a vial containing about 2 mmoles of each reactant. The vial was sealed (under nitrogen) with a self-sealing neoprene diaphragm and immediately transferred t o a constant temperature bath (55 =t0.1"). n-Pentane (0.3 ml.) was immediately injected into each reaction mixture by means of a hypodermic syringe thus providing a n internal standard for quantitative determination of olefinic products. The total operation required about 2-3 min.
[COSTRIBUTION FROM
THE
27.13
Analysis of Reaction Mixtures.-At the desired time, 0.5 nil. of the reaction mixture was withdrawn from the vial b y a precooled hypodermic syringe and injected into a neoprene-sealed vial containing a mixture of water and inert hydrocarbon. The sample was then cooled in t h e presence of Dry Ice. This removed the base and solvent from the hydrocarbon layer. The hydrocarbon layer was then sampled with a syringe and analyzed for the olefin in question on a gas chromatographic unit. This unit was a Perkin-Elmer Model 154 equipped with a 21 ft. DC-200 column (30 wt. ":; silicone oil, 0.25 in. in diameter). The unit was operated under 12 p.s.i.g. of helium in the temperature range of 40 t o 7 5 ' . All final yields of olefinic products were based on a t least tm-o g.c. determinations. Absolute olefin yields were determined from the g.c. area of the internal standard (n-pentane) and the area of the olefin in question; percentage yields were calculated on t h e basis of one mole of olefin/niole reactant in all cases. In those reactions which were unsuccessful or gave a low yield of olefinic product, analysis for the starting material was desirable. This was carried out on an F & 51.2 Flaine Ionization Unit (Model 609) equipped with a 2-it. siliccme rubber column (30 wt. c ) i ,0.25 i n . in diameter). This unit was temperature programmed a t g"/min. from 7,%250°. The latter conditions were also employed in the identification of niercaptans referred t o in Tables I and 11. Miscellaneous Experimental 'Methods.-In two cases starting materials were synthesized. %-Butyl disulfide was prepared from the reaction of the sodium salt of n-butyl mercaptan with iodine according t o the method described by \.ogel.S1 When isolated, the physical properties of the disulfide were identical to those recorded in Reid.** tert-Butyl sulfoxide was prepared by the oxidation of tert-butyl sulfide a i t h hydrogen peroxide in acetic acid ( m . p . G4', reportedz3m . p . 63.5-65").
Acknowledgment.--The authors are indebted to the Esso Research and Engineering Co., especially the Process Research Division, for the privilege of publishing this work. (21) E I Vogel, "Practical Organic Chemistry," Longmans Green a n d
C o . , S e w York, S Y . ,1939, pp 496-498 (22) E . E Reid, "Organic Chemist.ry of Bivalent Sulfur," Val Chemical Publishing Co , New York, N. Y . , 1960, p 396. (23) 1- Bateman, e l ai.,J C h e m . Soc , 5339 (1961).
DEPARTMEST OF CHEMISTRY, BUCKNELL UNIVERSITY, LEWISBURG, PA.,ASD UNIVERSITAT K O L N , KOLX,GERMASY]
The Isomerization of Aziridine Derivatives.
THE
111
CHEMISCHES ISSTITCTD E R
VI1
BY HAROLD W. HEINE RECEIVED M A Y1, 1963
Four new isomerizations of aziridine derivatives are described. They include the rearrangement of l-phenylthiocarbonylaziridine into 2-phenylthioethpl isocyanate or methyl S-2-phenylthioethylcarbamate and the isomerization of 1-(o-chloromethylbenzoy1)-aziridine into either N-2-chloroethylphthalimidineor l-(2-chloroeth\-limine)-phthalan. The reaction of equimolar quantities of phthaloyl chloride with aziridine to form S - 2 chlorcethylphthalimide is also reported.
Introduction Derivatives of aziridines have been isomerized into oxazolines, imidazolines, imidazolidinones, thiazolines, pyrazolines, triazolines, picramides, N-P,y-unsaturated amides, and anils. The present communication describes a number of new isomerizations of appropriately substituted aziridines into (1) an isocyanate, (2') an N-2-chloroethylphthalimide, ( 3 ) a phthalimidine, and (4) a phthalan. Results 1-Phenylthiocarbonylaziridine (I, N,N-ethylene-Sphenylthiocarbamate) is rearranged in refluxing xylene into the isomeric 2-phenylthioethyl isocyanate (11). The structure of I1 was established by analysis and by comparison of infrared spectra with an authentic sample prepared by reaction of 2-phenylthioethylarnine (111) with phosgene. The action of sodium iodide in methanol on l-phenylthiocarbonylaziridine a t room temperature gave methyl (1) Far a review of isomerizations of aziridines se? H W. Heine, Aitgeze,. C h e m . , 7 4 , 772 (1962); Angew Chem Z i z i r m a f Edit. Engi., 1, 528 (1962)
N-2-phenylthioethylcarbamate ( I V ) . The structure oi IV was confirmed by an independent synthesis involving the reaction of 2-phenylthioethyl isocyanate with methanol. A control run with I in methanol without sodium iodide gave a liquid residue whose infra;ed spectrum indicated mostly starting material, an isocyanate peak, and some of the peaks characteristic of the carbamate. After compound I was refluxed in methanol for 22 hr. the solvent was evaporated. :I white solid whose infrared sprctrum was identical with that of I V was obtained. However, this product had an odor characteristic of thiophenol.
Vol. 85
HAROLD LV. HEINE
2764
Another rearrangement, involving an aziridine as an unstable intermediate, was observed when equimolar quantities of phthaloyl chloride and aziridine were allowed to react in ether containing triethylamine. Filtration of the triethylamine hydrochloride formed followed b y ebullition of the filtrate for several hours gave N-2-chloroethylphthalimide (V) in 85y0 yield. The latter compound was identified by comparison of spectra and a mixture melting point with a genuine sample
0 q I I 6-e
2 I1
CeH6S-C-NCH2CH21
u fl
?..@
A~NHCN Nal ~ A ~ N H C N C H ~ C H--~-+ I
-
XIIa
0
0
In a related reaction of aziridine with o-chloromethylbenzoyl chloride the intermediate 1-(o-chloromethylbenzoyl)-aziridine (VI) can be isolated and isomerized in refluxing toluene into the corresponding N-2-chloroethylphthalimidine (1711). The product was characterized by analysis and by oxidation in excellent yield to the known N-2-chloroethylphthalimide (V) . 0
v
XIIb
ArN,c, NH U
XI11
formation of I into IV represents still another example of a rearrangement of an aziridine system that is catalyzed by a nucleophile.8-10 The thermal isomerization of I into I1 in refluxing xylene is analogous to the pyrolytic isomerization of 1-benzoylaziridine whereby 2-phenyl-2-oxazoline is obtained as the product. l 1 l 2 I t seems likely that the reaction between equimolar quantities of aziridine and phthaloyl chloride proceeds through an aziridine intermediate such as XIV A reaction for which a similar mechanistic pathway can be postulated is the interaction of 1-alkyl substituted aziridines with low molecular weight aliphatic acid anhydrides to yield ester amides For example, 1-n-butylaziridine reacts with acetic anhydride to pro' Ice l\;-2-acetoxyethyl-N-n-butylacetamide ' ? The in0 ii
IX
Irradiation of V I slowly transformed i t into an oil which could be distilled and which was isomeric with VI. The oil was assigned the structure 1-(2-chloroethy1imino)-phthalan (VIII) on the basis of analysis, chemical reactions, and infrared spectrum. The oil readily dissolved in dilute hydrochloric acid and formed a picrate which analyzed satisfactorily as a picrate of a substance isomeric with V I . Acid hydrolysis of the oil gave phthalide I X in i37? yield and 2-chloroethylamine hydrochloride. LIminophthalans have been observed to hydrolyze to p h t h a l i d e ~ . ~Furthermore, .~ the oil could be transformed into VI1 by prolonged heating in refluxing toluene. The conversion of imido esters into amides by heating is well documented. 4,j A11 these results are compatible with the structure VI11 for the oil. In addition, the infrared spectrum of VIII is quite similar t o phthalide and has two absorption peaks a t 5.62 and 3.80 ,u (Nujol). An oxazoline structure for VI11 is precluded by the fact t h a t 2-o-tolyl-2oxazoline absorbs a t significantly longer wave lengths, namely, 5.90and 6.03p .
Discussion The conversion of 1-phenylthiocarbonylaziridineby iodide ion in methanol to the carbamate I V can be envisaged as a nucleophilic attack on an aziridinyl carbon by the iodide ion to give the ion X . Displacement of the iodine of X by sulfur leads to the isocyanate I1 which subsequently reacts with the solvent to form the carbamate. The rearrangement is quite similar Gabriel. Be? , 2 0 , 2233 (1887). Gabriel a n d W. Landsberqer. ibid., 31, 2732 (1898). W C h a p m a n , J Che Soc , 1992 (1925); 2296 (1926)
0 II
ArNCNHCH2CHJ 8../I
V
(2) S (3) S f4) A (1927) (5) K
IV
A
XI
VI11
CHsOH
to the isomerization of 1-aziridinecarboxanilides ( X I ) into I-aryl-2-imidazolidinones( X I I I ) by iodide ion in acetone s ~ l u t i o n . ~In , ~ this case a tautomerization of the intermediate ion X I I a to the ion X I I b may occur prior to the internal alkylation step. The facile trans-
0
0
-
1719
B IViberg a n d B I Rowland, J . A m Chem. Soc , 77, 220.5 (1955)
QfC1
Y1 0
+
"3
n-~u~q
XIV
-t. (CH&O)20
- B ~ N ~
dl
CH3C- 0-CCHB /I II 0
-
0 ll
?
CH&N(~-BU)CHZCHZOCCH~
0
termediate XIV seems even more reasonable on the basis of the analogous isomerization of 1-(o-chloromethylbenzoy1)-aziridine (VI) into N-2-chloroethylphthalimidine (1711). Although internal N-alkylation of the intermediate X I V or of the compound VI would yield the observed products directly, one cannot discount a prior isomerization of XIV or VI to an oxazoline. The nitrogen atom of the oxazoline ring could in turn react with an (6) H W. Heine, W G Kenyon, and E M Johnson. rbid , 83, 2570 (1961) (7) H , Najer. R . Giudicelli. J Menin, a n d C. Morel. Compi r r n d ,
ass, 2 x 9 (1961). (8) H . W. Heine, M. E. F e t t e r , a n d E M . Nicholson, J A m . Chem Soc., 81, 2202 (19.59) (9) H W. Heine a n d H S Bender, J Org. Chem , 25, 461 (1960) ( I O ) H 1%' Heine and D A Tomalia. J . A m . Chem Soc , 84, 993 ( l y e ? ) ( 1 1 ) S Gabriel a n d K Stelzner, B e ? , 28, 2929 (1895) (12) A A Goldberg a n d W Kelley, J Chem Soc , 1919 (1948). (13) Badische-Anilin- und Soda-Fabrik Akt Ges , British P a t e n t 784,058, Ocl 2. 1957, C h e m . Abstr , 62, 5034h (1958)
Sept. 20, 1963
2'745
ISOMERIZATION OF AZIRIDINES
adjacent o-carbonyl chloride group or an o-chloromethyl group to form the reaction products. The reaction of 2-(p-nitrophenyl)-2-oxazolinewith benzoyl chloridei4 on a steam bath for 3 min. to yield N-(P-chloroethy1)N-benzoyl-p-nitrobenzamide lends support to this idea. The photochemically induced rearrangement of 1 -(o-chloromethylbenzoy1)-aziridineappears to be due to an energized oxygen atom which displaces the halogen from the o-chloromethyl carbon with formation of the phthalan VI11 as the product. LIminophthalans have also been isolated as products of pyrolysis of ochloromethylbenzamide and 2-chloromethyl-&nitrobenzamide.2 , 3 Experimental Phenylthiocarbonyl chloride was prepared by a modification of a published procedure.'j I n t o a solution of 17.7g. of thiophenol in 500 ml. of benzene cooled in an ice bath was bubbled 53.5 g. of phosgene which had been previously passed through concentrated sulfuric acid. T o this mixture was added portionwise and with stirring 46.0 g. of triethylamine. The mixture was stirred 1 hr. without the ice bath and the triethylamine l~ydrochloride filtered. The benzene was distilled a t atmospheric pressure under a hood. From the residue was obtained 49.6 g. of phenylthiocarbonyl chloride, b.p. 10il-104° (12 m m . ) . Redistillation gave a sharp boiling fraction a t 104" (12 m m . ) ilit.15 value 104' (13 m m . ) ) . 1-Phenylthiocarbonylaziridine (I).--A solution of 21.2 g. of pheiiylthiocarhonyl chloride in 150 ml. of dry ether \vas cooled in a n acetone-Dry Ice bath. T o this solution was added with vigorous shaking over a 10-min. interval a solution (previousllcooled in an acetone-Dry Ice b a t h ) of 5.3 g. of aziridine and 12.3 g. of triethylamine in 100 ml. of dry ether. .2 precipitate of triethylamine hydrochloride formed immediately. After the reaction mixture stood a t room temperature for 0.5 hr. t h e precipitate was filtered and the ether evaporated in a flask immersed in a water bath kept a t room temperature or below. A crude yield of 18.3 g. of I was obtained and recrystallized, usually immediately after isolation, from petroleum ether ( b . p . 40-70°), care being taken not t o keep the recrystallization flask on the hot plate too long. After filtration t h e solution was cooled in an acetone-Dry Ice bath. The recrystallized material melted at 39-4 1 O . Anal. Calcd. for CgHgNOS: C, 60.32; H , 5.06; N, 7.81. Found: C, 60.76; H , 5.08; S , 7.73. 2-Phenylthioethyl Isocyanate (II).-Phosgene (24.2 9 . ) was passed through concentrated sulfuric acid into a flask immersed in a n ice bath and containing 120 ml. of anhydrous toluene. The resulting solution was added quickly t o a well stirred solution of 11.0 g. of 2-phenylthi0ethylamine'~ in 120 ml. of toluene. A white precipitate formed immediately. The reaction mixture was stirred for an additional 30 min. and then refluxed gently for about 35 min. During this time the reaction mixture became clear. The toluene was distilled i n z'acuo and the residue vacuuni distilled. A crude yield of 8.7 g. of 11, b.p. 106-108" ( 0 . 5 m m . ) , was obtained. Redistillation gave material boiling a t 101" (0.25 m m . ) . Anal. Calcd. for C 9 H s S O S : C, 60.32; H , 5.06; N , 7.81. Found: C, 60.50; H , 5.07; S, 7.73. Isomerization of I into II.-A mixture of 8.2 g. of I and 200 ml. of anhydrous mixed xylenes was refluxed in a dry atmosphere for :j days iii a n oil bath held a t 200'. A11 b u t about 10-15 ml. of the solvent was removed b y vacuum distillation. The residue was placed i n a n addition tube and the remaining solvent flashed off under vacuum by dropwise addition into a distillation flask immersed in a n oil bath held a t about 80". The residue in the distillation flask was distilled t o yield 5.1 g. of 11, b.p. 83-87" ( 0 . 1 inm.). The infrared spectrum was identical with the material prepared by reaction of phosgene with 2-phenylthioethylamine. If the reaction mixture was refluxed for less than 3 days the distillate contained some unreacted I as was evident by examination of the infrared spectrum. Methyl N-2-Phenylthioethylcarbamate (IV). Method A.-A mixture of 0.5 g . of 2-phenylthioethyl isocyanate and 0.5 g. of anhydrous methanol was kept at room temperature for 1 hr. The methanol was evaporated and the solid remaining was slurried with petroleum ether (b.p. 40-70') and filtered. The crude 11. weighed 0.4 g. and melted a t 60-62'. Recrystallization from petroleum ether gave material melting a t 66-67". ( 1 4 ) E >I F r y , J O i g Chem , 16, 802 ( 1 9 5 0 ) . (1.7) H Rivier, Bioi soc c h i m , ( 4 1 1, 733 ( 1 9 0 7 ) . (16) A E S e n e a r . >I .\IR a p p o r t , a n d J B Koepfli, ?2!4 ( 1 9 4 7 )
J Bioi. Chem
, 161,
Anal. Calcd. for CIOHIJSO*S:C , 56.88; H , 6.19; S ,fi.fX3 Found: C , 56.86; H , 6 . 2 4 ; S , 6 . 5 0 . Method B.-Four grams of sodium iodide was added t o a solution of 1.00 g. of I and 20 ml. of methanol. The rcartioii mixture became warm. i\fter standing overnight at room temperature the solvent was evaporated and the residue washc(l with cold water and filtered. The crude 11' weighed 1.05 g. and melted a t 58-64'. Recrystallization gave crystals identical with t h a t prepared by method A . Reaction of Phthaloyl Chloride with Aziridine.--I\ solution of 4.1 g. of phthalo) 1 chloride in 50 ml. of benzene was added tiropwise t o a solution of 0.86 g . of aziritiitie ant1 2.02 E . of trietlivlamine in 50 nil. of benzene. The precipitatc of ~ r i c t h y l a t i i ~ n c hydrochloride was filtered and washed with 50 nil. of benzene. The combined filtrates \\-ere refluxed for 1.5 h r . a n d tht. solvent evaporated. The yield of crude S - ~ - c h l o r o e t l ~ ~ l p l i t l i a l iwas ~~~ide 4.3 g. and melted a t 7-1-77'. A sample rccrystallizetl from ethanol melted a t 79-81' and had an infrared spectruni itlrntical with that of a n authentic sample. 1-(o-Chloromethylbenzoy1)-aziridine (VI).cooled solution of 2.15 g . of aziridine and 5.06 g. of triethylamine in fi0 i i i l . of d r r ether was added portionu-iseover 10 min. t o a cold solution of 9.45 g. of o-chlorotnethylbenzoyl chloride" in 60 nil. of d r y ether. The reaction mixture was filtered and the filtrate evaporated. The 8.4 g. of crude V I was immediately slurried with 10 nil. o f cold 9572 ethanol and filtered. The coinpound was t\:.icc recrystallized from a small quantity of 95t.i ethanol a t 3 - 3 5 " . The recrystallized 1.1 melted at 52-53.5'. I t is important t o purify the crude \'I a t once and t o store it in a refrigerator. Anel. Calcd. for CloHlaCISO; S ,7.16. Fouiid: S ,6.80. Isomerization of VI to N-2-Chloroethylphthalimidine(VII) .A mixture of 2.5 g . of 1.1 and 40 ml. of dry tolucrie \vas refluxed 15 hr. The solvent was evaporated and the residue of light yellow crystals weighed 2.5 g. Recrystallizatioti from petroleum ether gave material melting a t 81-83'. Anal. Calcd. for CI,,HloCINO: N,7.16. Found: N, 6.95. Oxidation of VI1 to N-2-Chloroethylphthalimide.--Xsolution of 2.0 g. of sodium dichromate in 5 ml. of water was added carrfully t o a solution of 0.7 g. of 1.11 in 2 nil. of cold concentrated sulfuric acid. Much heat was evolved. The reaction mixture was refluxed for 30 min., then cooled, diluted with 3 nil. of water, and filtered. The residue weighed 0.Sc5g. and had :in infrared spectrum t h a t was identical with that of an authentic sample of X-2-chloroethylphthalimide. The crude product i w s recrystallized from 9 5 ' i ethanol and melted at 80-83". Isomerization of VI to 1-(2-Chloroethylimino)-phthalan iVIII I. -Four grams of 1.1 was placed in a test tube and exposed t o ultraviolet irradiation supplied by a Hanovia mercury iirc type 16106 and equipped with a Corning filter 7-37 for .i d a y s . ?'lie transformation also takes place with sunlight hut ith a reaction time of about 2 weeks. The solid 1.1 gradually changed t o a dark yellowish green oil. An infrared spcctru~nof this crude \.I11 indicated complete conversion of the starting material. 1)istiIl:ition of the crude oil was diflicult b u t could be accomplished by a rapid distillation a t high vacuum. The boiling point of \ ' I l l was 11&116" (0.26 m m . ) . If t h e distillation \vas attempted at a higher temperature the iriiinophthalan convcrts into \.I I . The spectra of the crude and the redistilled \'I11 were idcntical. Anal. Calcd. for CloHloCISO: S , 7.lf;. Fnuiid: S ,fi.70. The picrate of 1.111 decomposed a t 175-182' after recrystallization from ethanol. Anal. Calcd. for C16HlaCIS40x:S, 13.19, Found: S , 13.00. Hydrolysis of VII1.-One gram of 1.111 was refluxed 10 h r . with 20 ml. of lo(,; hydrochloric acid. The reaction iriisturc. was extracted three times with ether and the ether extracts \ w r c evaporated t o yield 0.50 g. ( 7 3 ( i )of phtlialide which was identified by comparing with a genuine sample. Evaporation of the aqueous layer gave deliquescent crystals which were placed i n a vacuum desiccator for several days. .In infrared sjicctruni of this material was identical with t h a t of a comtiierci:il sample of 2 chloroethylarniiie hydrochloride. No yield \vas recorded. Isomerization of VI11 to VI1.-In one instance a i i attciiiptrd distillation of 1.11 a t 8 nitii. converted a11 of it to n solid ill the distillation flask. The solid \\-asshown to be \ ' l l by melting point, mixture melting point, and infrared spectrum. I u another experiment 0.93 g. of 1.111 in 8 0 nil. of toluetie \vas refluxed for 3 days. Evaporation of the solvent and seeding of tlrc residual oil with 1'11 caused solidification. I ~ c c r y s t a l l i z a t i oo ~f ~ the crude \.I1 gave 0.43 g . of material melting a t ;-XI '.
Acknowledgment.-The author wishes to express his appreciation to the National Science Foundation for a Senior Faculty Fellowship and to Professor Emanuel (17) I G. H i n t o n , F G I l a n n . and 4 ( 1 959 i
Vanterprml .I
i'hriti
4w
fill)
T G TRAYLOR A N D X LT BAKER
2746
Vogel for a delightful year a t the University of Koln, where a part of this work was accomplished. The author thanks h l r . Donald Tomalia for the initial syn-
[CONTRIBUTIOSFROM
THE
Vol. 85
thesis of 1-phenylthiocarbonylaziridine and for an experiment of this material in moist acetone containing sodium iodide.
CHEMISTRY DEPARTMEST O F THEUNIVERSITY O F CALIFORNIA, S A S DIEGO,LA JOLLA, CALIF, A N D THED O W CHEMICAL CO , PITTSBURG, CALIF]
The Oxymercuration of Olefins. I. A General Method for Determination of the Stereochemistry of Oxymercuration BY T. G. TRXYLOR A N D A. u'.BAKER RECEIVED MARCH30. 1963 The addition of mercuric salts t o olefins in water produces hydrosymercurials, HOCR2CR2HgX, whose OH stretching frequency differs from t h a t of the parent alcohol, HOCR2CRrH,by an amount which depends on the mercury-oxygen distance. The frequency difference, A v , amounts to 6-10 cni. for either open chain or trenshydroxymercurials; cis-hydroxytnercurials show a A u of 18-22 cni. - l . Consequently, it is possible to deduce the stereochemistry of oxymercuration from the OH stretching frequency of the product. Using this technique, and other methods for corroboration, we have confirmed our previous conclusion that, although cyclopenterie and cyclohesene form tinns-OxSmercuration products, norhornene is ox5mercurated exclusively cis-eso. Because the latter result is anomalous on two counts, \\-e have extended this finding to dicyclopentadiene and benznorhornene, concluding t h a t such strained olefiris generally add mercuric salts ivithout rearrangement to afford exclusively e m - r i s products. These findings are incorporated into previously proposed mechanisms of electrophilic addition. Structural effects responsible for changes in stereochemistry of addition are discussed.
Introduction The similarity of oxymercuration to other electrophilic olefin addition reactions is well established.
place mercury by hydrogen. Typical reductions are illustrated in eq. 2 and 3 for the norbornene adduct.
R ~
0
The addition is first order in mercuric salt, first order in olefin, and is stereospecific.' The products of this addition to cyclopentene and cyclohexene have been demonstrated to have trans configurations by their elimination rates, 2 , dipole moments,4 and nuclear magnetic resonance spectra.j Therefore, the recent observation that norbornene adds mercuric salts to give the exo-cis configuration6 seems to warrant further investigation of olefin oxymercuration, especially the oxymercuration of strained and bicyclic olefins. IVe have consequently undertaken the tasks of establishing the generality of the cis addition in 2.2.1-bicyclic olefins and of determining whether this change from complete trans-oxymercuration to complete cis-oxymercuration with change in olefin structure is due to olefin angle strain or some more specific property of bicyclic systems. This paper reports our progress on the former along with some conclusions concerning the mechanisms of ionic additions to olefins. In order to pursue efficiently the stereochemistry of the addition reaction with a variety of olefins it was necessary to develop a simple, general method of structure proof. This proof must establish the skeletal structure, the -OR configuration, and the position and configuration of the mercury atom. The first of these can usually be accomplished by reducing the mercurial with sodium amalgam' or sodium b o r ~ h y d r i d e " to ~ re(1) J . C h a t t , C h e m R e v , 48, 7 (19.51). :2 hI 31 Kreevoy a n d F R K a w i t t , J A m Chem. S o c , 8 2 , 739 (1960) (ti) T G Traglor and S IVinstein, Abstracts, 133th S a t i o n a l 3Ieeting of the American Chemical Society, Boston. 1 I a s s , April, 1959, p. 8 2 - 0 (4) ( a ) A G . Brook, R Donovan, a n d G F W r i g h t , C a n . J C h e m , 31, ,536 (1953), ( h ) although these authors interpret their dipole moment results as indicating c t s addition. they are clearly more consistent with l r a n s . (,j) h l M Anderson a n d P. M H e n r y , Chet!? I n d ( L o n d o n ) , 20.53 ( 1 Q l i l ) . (Ci) T G Traylor a n d A I\-. Baker, 7 ' e l v u h ~ i i i . o ~Letters, i No. 19, 1 i (1959) ( 7 ) (ai J S a n d a n d F. Singer. Rei., 3 5 , 3170 ( 1 9 0 2 ) . ( h ) A I I M, 339, 181 [ 190:3> (8) J H . Rohson a n d G F Wright. C-un J . C h e m , 38, 2 1 (19Ci0) (9) H . B Henbest a n d B Piicholls, J . C h e m . SOC., 227 (1959)
eq. 3
LVe have occasionally employed sodium borodeuteride or sodium amalgam in DzO to afford additional stereochemical evidence (eq. 4). Identification of the resulting alcohol with a known alcohol establishes the skeletal structure and configuration of the OH (or OR) group. The position of the mercury atom can be ascertained by the deuterium replacement shown in eq. 1,by the n m.r. spectrum of the mercuria1,jor by a less equivocal process of oxidizing the alcohol with permanganate to a ketone"' in which the mercury is enolizable only if it is D to the ketone group" (eq. 5 ) .
\Ve have employed all three methods. The configuration of the mercury atom relative to the OH group can be inferred from rates of elimination in acid2 or from dipole moment measurement.4a,b This configuration can be established in some cases (e.g., in T'II) from the n.m.r. coupling constant between protons attached to the carbon atoms in question.b Rut the most general and convenient method for demonstrating the stereochemical relationship of these two groups is the infrared method presented here. 110) I . F 1,utsenko a n d R I Sivkova, Z h . Obshchet K h i w . , 39, 1189 (19\59) (11) 0 A Reutov and L T. Chzhu, Doki. d k a d V a u k S S .S R , 110, 575 (1956).
